在Rails中的3个表之间建立数据库连接

Question

i can't seem to find a straight forward answer so let me explain what i'm trying to do with my example:

I'm trying to connect 3 tables together, i have Users Artists and Events

Now what im trying to do is make a huge spiderweb here, the plan is to have the user follow the artist and/or event.

The artist belongs to an event (there can be many artists to an event)

This is where i start to get confused. How do i go about making this work so that the user is connected to the event/artist depending on who/what they follow? (this is done in the view, the user goes to the event page and can click a stay updated button which would then save either the eventid or artist id to be used later.

What i don't get is,

What columns do i need to make in the database,

What do i need to do to the models to link them all together?

All my models are currently empty.

Answer 1

This is a has_many :through association. The Rails Associations guide is very detailed on this topic, so check it out for an in-depth explanation.

Let's start with the Artists and Events tables.

An artist can play at many events, and an event will have many artists. To implement this relation a third table called EventArtists which keeps track of which events have which artists is needed, and which artists play at which events.

You can have multiple artists for one event (EventID 1), and a repeating artist (ArtistID 1) participating at multiple events.

EXAMPLE:

EventsArtists 
-----------------
ArtistID EventID
1        1
2        1
1        2

Your EventArtists will have a minimum of the two columns listed in the table above, which are ArtistID and EventID .

Your models will then look like the following.

class Artist < ApplicationRecord
has_many :event_artists
has_many :events, through: :event_artists

class Event < ApplicationRecord
has_many :event_artists
has_many :artists, through: :event_artists

class EventArtist < ApplicationRecord
belongs_to :artist
belongs_to :event

To add a Users table into the mix, you must create UserArtists and UserEvents .

Note : Table names such as UserArtists could be instead be named Follows - it all depends on what you think is clear.